In adult patients with transient loss of consciousness presenting to an ED, what features of the history point to a diagnosis of NMS?

Report By: Markus Arnold - Medical Student

Institution: Manchester Royal Infirmary

Date Submitted: 9th July 2011

Last Modified: 21st July 2011

Status: Blue (submitted but not checked)

Three Part Question

In [adult patients with transient loss of consciousness presenting to an ED], [what features of the history] point to a [diagnosis of NMS]?

Search Strategy

Medline (1948 to June Week 4 2011) and Embase (1980 to week 26 2011) using the Ovid interface.
{[(transient loss of consciousness.mp.) OR (TLOC.mp.) OR (T-LOC.mp.) OR (exp Unconsciousness/) OR (exp Syncope/)] AND [(history.mp.) OR (features.mp.) OR (History/) OR (exp Medical History Taking/)] AND [(neurally mediated syncope.mp.) OR (reflex syncope.mp.) OR (vasovagal.mp.) OR (simple faint.mp.) OR (faint.mp.) OR (exp Syncope, Vasovagal/)]} LIMIT to humans AND english language.

Search Outcome

In Medline 341 papers were found of which 3 were relevant. In Embase 2442 papers were found, of which 2 were relevant, 3 were duplicates and two were deemed to be of insufficient quality to be included.

Relevant Paper(s)

Author, date and country

Patient group

Study type (level of evidence)

Outcomes

Key results

Study Weaknesses

Asensio, E., et al2003Mexico

117 consecutive patients referred for investigation of syncope over a 3 year period. 20 other patients had been excluded after cardiologist interview due to syncope of non-vasovagal cause.
The most frequent variables of the histories were compared to the HUTT result.

Excluding 20 patients may introduce a bias into the results.
No attempt to validate results
No reference to ethical approval.
No reference to statistical power.

Sheldon, R., et al2006Canada

418 patients were recruited over a 78 month period from 3 centres. Patients were included if they had a confirmed or working diagnosis of syncope, and excluded if there was history of heart disease or epilepsy. These patients were however used as part of a larger study on T-LOC.
118 variables were recorded from each patient and used to derive the Calgary Syncope Symptom Score.

380 patients from a single hospital over a 26 month period were used in the study. Patients presenting with T-LOC aged ≥18 were eligible, and excluded for a history of heart disease or epilepsy.
The outcome of each patient was compared to that predicted by the Calgary Syncope Symptom Score.

341 patients were analysed over a six month period from the syncope unit of three hospitals. 191 patients had suspected or certain heart disease, and 146 did not.
46 variables were collected from each patient and compared to the results of the HUTT.

Prospective cohort study

Patients with heart disease

Aim of study not entirely in line with the clinical question, as such it is hard to analyse the results of the entire group.
Relative lack of patient demographics.
No reference to statistical power.
No reference to ethical approval.

Abdominal prodrome: Sensitivity for NMS

8%

Abdominal prodrome: Specificity for NMS

99%

>4 years between first and last episode: Sensitivity for NMS

40%

>4 years between first and last episode: Specificity for NMS

87%

Nausea on recovery: Sensitivity for NMS

14%

Nausea on recovery: Specificity for NMS

96%

Patients without heart disease

>10 second prodrome: Sensitivity for NMS

39%

>10 second prodrome: Specificity for NMS

70%

≥3 episodes: Sensitivity for NMS

68%

≥3 episodes: Specificity for NMS

50%

Kulakowski, P., et al2005Poland

202 patients who were admitted to the syncope unit to be investigated for NMS. All had symptoms that had let referring doctors to suspect NMS.
A 34 question questionnaire was used to collect historical information and this was compared to the HUTT result.

Prospective cohort study

≥-2 points in whole group: Sensitivity for positive HUTT

78%

Results obtained from reading graph, poor presentation of results.
No reference to statistical power.
No reference to ethical approval.
No external validation.

≥-1 points in subgroup with >2 episodes in the last month: Sensitivity for positive HUTT

88%

≥-1 points in subgroup with >2 episodes in the last month: Specificity for positive HUTT

92%

Comment(s)

The available pieces of evidence for the most relevant historical features of NMS and any possible decision rule are hard to compare against each other. The five studies examined have slightly different aims and outcomes, plus are not based in an ED setting, so the focus is more towards a diagnosis rather than risk stratification. In the context of a wider ED guideline it should be noted that high risk patients should have already been identified in a screen for cardiac disease, so perhaps the low specificity of some of these results is less of a concern.
The recent guideline on T-LOC published by NICE commented on similar difficulty and took the route of a more general recommendation involving clinical judgement, and a system used by the DVLA for its ease of remembrance.
A reasonable compromise considering the would seem to be to take a middle ground of the Calgary Syncope Symptom Score and the NICE guideline's approach of 3 P's (posture, provoked, prodrome) with no features suggesting an alternative diagnosis.

Clinical Bottom Line

Discharge a patient in the presence of one of a) posture (symptoms brought about by prolonged standing), provoking factor (symptoms brought about by a reasonable factor i.e. needlesticks) or prodrome (i.e. sweating or warmth beforehand) and all of b) no history of heart disease, no features suggesting an alternate diagnosis and their first episode being before 35 years of age.